Josephson current oscillation in a Rashba ring.

We propose to use Rashba spin-orbital coupling (RSOC) to modulate the Josephson current in a one-dimensional ring-SQUID (superconducting quantum interference device) without any magnetic field or magnetic material. Supercurrent oscillation due to spin-dependent quantum interference of spin wavefunctions passing through the two arms of the ring in the presence of RSOC is found. A pure spin current flows in the system's ground state without a supercurrent due to the combined effect of the RSOC precession phase and the electron traveling phase caused by the asymmetry in the two arms of the ring. This purely electrical means of modulating the supercurrent by varying the RSOC will be useful for designing novel superconductor devices.